Et tu, Brute?

An endorsement, and what follows it, speaks not just to the object of the endorsement, but also the person making it.

In recent days, New Jersey Gov. Chris Christie and former New Hampshire Gov. John Sununu have been spotted taking former Massachusetts Gov. Mitt Romney’s opponents to task, going toe-to-toe with leftists on the ground and in the media, and generally acting as aggressive and persuasive advocates of their chosen candidate. Similarly, when Sheriff Joe Arpaio — “America’s toughest sheriff” — tossed his support behind Rick Perry’s immigration plan, he displayed solidarity with the Texas executive, taking to the Iowa campaign trail to make the case for his man.

When these leaders made the decision to back a candidate, they laid their principles and loyalty on the line. An endorsement is an important thing and says a lot about a person’s character.

Sometimes — as in the case of former Pennsylvania Sen. Rick Santorum’s 2008 endorsement of Mitt Romney — what an endorsement says about a person’s character is less than flattering. In 2006, in a push to appear more moderate before his crushing 17-point loss to Democrat Bob Casey, Santorum sought the endorsement of his colleague, Sen. John McCain. Just two years later, when McCain fought a primary battle against Romney, Santorum threw his support behind Romney. Citing the importance of maintaining the united conservative coalition built by former President Ronald Reagan, Santorum wrote, “Romney is the candidate who will stand up for the conservative principles that we hold dear … and he is the clear conservative candidate that can go into the general election with a united Republican party.”

So it wasn’t a surprise when McCain leapt to endorse Romney just hours after Santorum’s near-win in last week’s Iowa caucuses.

But this sort of political backstabbing is nothing new. From former President Teddy Roosevelt to former Clinton adviser Rahm Emanuel, the history of modern endorsement tomfoolery is storied.

In an email to The Daily Caller, historian David Pietrusza recounted some of American political history’s strangest bedfellows:

The most spectacular example of [endorsement] betrayal is former President Teddy Roosevelt forcing William Howard Taft on the GOP as the nominee in 1908, and then pillorying his friend Taft and running against him in 1912.

In 1920, Democrat Franklin Delano Roosevelt wanted Republican Herbert Hoover to be a Democratic nominee and even to be his running mate. He sent an emissary to Hoover to cajole him into that scenario.

Then, in 1932, FDR ran against Hoover in a vicious campaign in which he blamed Hoover for the Great Depression and helped popularize the term “Hooverville,” a reference to the shanty towns that popped up after the Wall Street Crash of 1929.

In 1944, Pietrusza continued, FDR’s soon-to-be successor, the hapless Sen. Harry Truman, “promised South Carolina’s Jimmy Byrnes he would deliver Byrnes’ nominating speech for FDR’s vice president. Instead, Truman ended up as FDR’s vice presidential nominee” and, when FDR died in office, Truman became the 33rd president of the United States.

Pietrusza explained that four years later Thomas Dewey, who was running again after losing to FDR in 1944, was attacked by his old running mate when Sen. John Bricker “backed his old buddy, Sen. Robert A. Taft, over Dewey in the Republican primary.”

In fact, the vice presidency has never seemed to engender much loyalty in the executive. Republican President Dwight Eisenhower, Pietrusza wrote, was once “asked to recall one decision he had made that Nixon had assisted him on. It was the last question of the press conference, and Ike said he get on that in a week. Never did. … Ike campaigned for Nixon at the end, but even when Ike left the voting booth he wouldn’t say who he had voted for.”

More recently, the Hillary Clinton campaign sparked some unusually public political infighting. When, in March 2008, New Mexico Gov. Bill Richardson — who had served in two senior position in President Bill Clinton’s administration — endorsed Barack Obama for president, senior Democratic analyst James Carville did not hold back, saying, “Mr. Richardson’s endorsement came right around the anniversary of the day when Judas sold out for 30 pieces of silver, so I think the timing is appropriate, if ironic.” Former Bill Clinton senior staffer Rahm Emanuel also failed to endorse Hillary Clinton in the 2008 primary, causing more than a few disagreements in Democratic ranks.

In an oft-paraphrased observation, Britain’s Lord Palmerston said, “We have no eternal allies, and we have no perpetual enemies. Our interests are eternal and perpetual, and those interests it is our duty to follow.”